Security company i-sec has demonstrated that a directional antenna made with a Pringles can significantly improves the chances of finding the wireless computer networks being used in London's financial district.

An informal survey carried out by i-sec using the homemade antenna has found that over two-thirds of networks were doing nothing to protect themselves.

The security firm said all the companies at risk could easily thwart anyone that wanted to find and penetrate their network by making a few simple changes to the hardware used to build the wireless networks.

Hack here

In November last year BBC News Online was shown just how easy it is to find and gain information about wireless networks.

People have made these antenna out of Pringles tubes, coffee cans and even old satellite dishes

Geoff Davis, i-sec

These networks are rapidly becoming popular because they are cheap, easy to set up and replace the unsightly cables that many companies have used to link PCs together into networks.

But the convenience of using radio waves to transfer data between machines is not without its risks.

Many curious hackers have started carrying out so-called war-driving expeditions.

US security expert Peter Shipley invented the practice. It involves driving around an area using a laptop fitted with a wireless network card to find and map out the networks.

Crisp signal

Wireless, or WiFi, networks have an encryption system built in, but it is not turned on when the basic hardware of the network is set up. Geoff Davies, managing director of i-sec, said its informal survey revealed that 67% of the networks it found had this encryption system turned off.

"Many companies are going out and buying a wireless access point to see what it can do," said Mr Davies. "The problem is that they have opened a great big back door into their network."

He said that i-sec had boosted the chance of spotting networks by converting an empty can of Pringles into a directional, or Yagi, antenna. Plans to make such an antenna first appeared on the net last year.

Properly made, such an antenna can boost signal strengths by up to 15 decibels, vastly aiding the discovery of wireless networks.

Potential for havoc

In one 30-minute journey using the Pringles can antenna, witnessed by BBC News Online, i-sec managed to find almost 60 wireless networks.

"People have made these antennae out of Pringles tubes, coffee cans and even old satellite dishes," said Mr Davies.

"Those doing [war-driving] are not necessarily looking to take down corporate networks, they are looking to use corporate bandwidth," said Mr Davies.

"But if they are doing that then someone with more nefarious purpose could wreak havoc."

Mr Davies said that a few basic steps such as changing default names, moving wireless access points to the centre of a building and switching off the networks' broadcast functions could help significantly improve the security of these systems.

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Most users will require a high gain antenna to provide good reception/performance from their system.  A low cost alternative to production antennas is the "Pringles" antenna built from some tapped bar, washers and the famous potato chip container - and it works. 

Equipment  

• Tapped rod, 5 5/8" long, 1/8" OD
• two nylon lock nuts
• five 1" washers, 1/8" ID
• 6" aluminum tubing, 1/4"
• IDA connector to match your radio pigtail
  (we used a female N connector)
• 1 1/2" piece of 12 gauge solid copper wire
  (ground wire from house electrical wiring)
• A tall Pringles can  (any flavour)
• Scrap plastic disc, 3" across
  (like another Pringles can lid)

There are two parts to the antenna made from the top and tube of the container.

Modify the top

1) Solder a short length of stout copper wire (earth cable from electrical cable will do) into the end of an N-type female connector.
2) Make a hole 86 mm up from the base of the tube and fix the connector into the tube.
The connector and wire should look like this when inserted into he tube. (The wire should be just short of the centre axis of the container) .

Modify the top

3) Cut four pieces of aluminum tube exactly 31 mm long.

4) Make a disk of cardboard (or similar) the same diameter as the inside of the tube. This will be used as a support inside the tube. (Trim the edge off a second lid).  

5) Make a hole in the centre of the disk and fit it over one of the four short aluminium sections.

6) Cut a piece of threaded bar 143mm long.

7) Make a kebab on the threaded bar of:- Nylon nut, washer, tube, washer, tube fitted with disk, washer, tube, washer, tube, washer top of contain nylon nut. Push the top onto the tube.  The wire should NOT touch any part of the lid construction.  Connect and communicate! Remember, this antenna is polarized.  The signal enters from the plastic lid.  When pointing the lid of this antenna at the base station it is likely that the connector will have to point up or down to give the best reception - but experiment!